Sorry for a long time break of the discussion about this problem.
Till now, I found one possible reason cause this problem.
The main reason of this problem is the splitted region could be online again.
The following is my anylysis:
(The cluster has two HMatser, one active and one standby)
1.While the active HMaster shutdown, the standby one would become the active
one, and went into the processFailover() method:
if (regionCount == 0) {
LOG.info("Master startup proceeding: cluster startup");
this.assignmentManager.cleanoutUnassigned();
this.assignmentManager.assignAllUserRegions();
} else {
LOG.info("Master startup proceeding: master failover");
this.assignmentManager.processFailover();
}
2.After that, the user regions would be rebuild.
Map<HServerInfo,List<Pair<HRegionInfo,Result>>> deadServers =
rebuildUserRegions();
3.Here's how the rebuildUserRegions worked. All the regions(contain the
splitted regions) would be added to the offlineRegions of offlineServers.
for (Result result : results) {
Pair<HRegionInfo,HServerInfo> region =
MetaReader.metaRowToRegionPairWithInfo(result);
if (region == null) continue;
HServerInfo regionLocation = region.getSecond();
HRegionInfo regionInfo = region.getFirst();
if (regionLocation == null) {
// Region not being served, add to region map with no assignment
// If this needs to be assigned out, it will also be in ZK as RIT
this.regions.put(regionInfo, null);
} else if (!serverManager.isServerOnline(
regionLocation.getServerName())) {
// Region is located on a server that isn't online
List<Pair<HRegionInfo,Result>> offlineRegions =
offlineServers.get(regionLocation);
if (offlineRegions == null) {
offlineRegions = new ArrayList<Pair<HRegionInfo,Result>>(1);
offlineServers.put(regionLocation, offlineRegions);
}
offlineRegions.add(new Pair<HRegionInfo,Result>(regionInfo, result));
} else {
// Region is being served and on an active server
regions.put(regionInfo, regionLocation);
addToServers(regionLocation, regionInfo);
}
}
4.It seems that all the offline regions will be added to RIT and online again:
ZKAssign will creat node for each offline never consider the splitted ones.
AssignmentManager# processDeadServers
private void processDeadServers(
Map<HServerInfo, List<Pair<HRegionInfo, Result>>> deadServers)
throws IOException, KeeperException {
for (Map.Entry<HServerInfo, List<Pair<HRegionInfo,Result>>> deadServer :
deadServers.entrySet()) {
List<Pair<HRegionInfo,Result>> regions = deadServer.getValue();
for (Pair<HRegionInfo,Result> region : regions) {
HRegionInfo regionInfo = region.getFirst();
Result result = region.getSecond();
// If region was in transition (was in zk) force it offline for reassign
try {
ZKAssign.createOrForceNodeOffline(watcher, regionInfo,
master.getServerName());
} catch (KeeperException.NoNodeException nne) {
// This is fine
}
// Process with existing RS shutdown code
ServerShutdownHandler.processDeadRegion(regionInfo, result, this,
this.catalogTracker);
}
}
}
AssignmentManager# processFailover
// Process list of dead servers
processDeadServers(deadServers);
// Check existing regions in transition
List<String> nodes = ZKUtil.listChildrenAndWatchForNewChildren(watcher,
watcher.assignmentZNode);
if (nodes.isEmpty()) {
LOG.info("No regions in transition in ZK to process on failover");
return;
}
LOG.info("Failed-over master needs to process " + nodes.size() +
" regions in transition");
for (String encodedRegionName: nodes) {
processRegionInTransition(encodedRegionName, null);
}
So I think before add the region into RIT, check it at first.
Thanks!
Jieshan Bean
--------------------------------
I didn't run the hbck to check the system. The environment has been recovered
now, so I need to recreate the problem,and run then run hbck, maybe it could
give some helpful information.
Thanks!
Jieshan Bean
-------------
Can you run hbck?
J-D
2011/5/17 bijieshan <[email protected]>:
> Yes, you're right. While count the .META., the result will exclude the -ROOT-
> region and the .META. region. Pardon me ,I should not mention about that.
> Maybe the less 2 region is just a coincidence here, I can show another
> scenario about this problem:
>
> From WebUI, we can see that:
>
> Address Start Code Load
> C4C3.site:60030 1305620850621 requests=0, regions=10227, usedHeap=2161,
> maxHeap=8175
> C4C4.site:60030 1305620851291 requests=0, regions=10234, usedHeap=2593,
> maxHeap=8175
> C4C5.site:60030 1305620851505 requests=0, regions=10227, usedHeap=2191,
> maxHeap=8175
> Total: servers: 3 requests=0, regions=30688
>
> From HMaster logs:
>
> 2011-05-18 10:06:08,382 INFO org.apache.hadoop.hbase.master.LoadBalancer:
> Skipping load balancing. servers=3 regions=30681 average=10227.0
> mostloaded=10227 leastloaded=10227
> 2011-05-18 10:06:13,365 DEBUG org.apache.hadoop.hbase.zookeeper.ZKUtil:
> hconnection opening connection to ZooKeeper with ensemble
> (C4C3:2181,C4C2:2181,C4C1:2181)
>
>
> 30681 & 30688
>
> 7 region differ from this scenario.
>
> Thanks!
>
> Regards,
> Jieshan Bean
>
>
> ----- -----
> Re: Regions count is not consistant between the WEBUI and LoaderBalancer
>
> .META. does not include region information for itself or -ROOT- so a count
> of .META. should always be two regions less than the total number.
>
> -chris
>
> On Tue, May 17, 2011 at 4:32 AM, bijieshan <[email protected]> wrote:
>
>> This problem seems happened with high probability, I have saw it several
>> times.
>>
>> Here's the description about this problem:
>>
>> 1.From the WEBUI, I can see the regions count is:35087.
>> 2.From the HBase shell, I counted the '.META.' table, and it showed there's
>> 35085 regions.
>>
>> hbase(main):001:0> count '.META.',10000
>> 11/05/14 14:12:22 INFO jute.BinaryInputArchive: Expecting maxBufferString
>> as an integer but got as null.Hence setting to default value 1048575
>> Current count: 10000, row:
>> hello,080472,1305272720373.ec0eb8c1bb414967241155cf0985241e.
>> Current count: 20000, row:
>> hello,161272,1305272956858.e16008645368590dfa735abc61024db6.
>> Current count: 30000, row:
>> ufdr,061870,1305171874909.eddc77cbfa2f93feef49f4485d9b88a5.
>> 35085 row(s) in 2.5250 seconds
>>
>> 3.From the HMaster logs, I saw that:
>>
>> 2011-05-14 14:13:57,546 INFO org.apache.zookeeper.ClientCnxn: EventThread
>> shut down
>> 2011-05-14 14:14:01,303 INFO org.apache.hadoop.hbase.master.LoadBalancer:
>> Skipping load balancing. servers=4 regions=35089 average=8772.25
>> mostloaded=8773 leastloaded=8773
>> 2011-05-14 14:14:08,706 DEBUG
>> org.apache.hadoop.hbase.master.CatalogJanitor: Scanned 35085 catalog row(s)
>> and gc'd 0 unreferenced parent region(s)
>>
>> 35087 & 35085 , so where's the problem? Were they from the different sets?
>>
>> Thanks!
>>
>> Regards,
>> Jieshan Bean
>>
>>
>>
>>
>
